Flotation



.from the more valuable mineral.

am Aug. 24, 1 43 UNITED STATES PATENT oF-Ficr.

Edward J. Ellis, Bartow, Fla,

ern Phosphate Corporation, a corporation of Delaware Application April 1, 1941, erial No. 386,309

3' Claims. (or. 209-166) No Drawings.

This invention is concerned minerals by flotation processes employing cationic reagents and aims to improve the selectivity-of such processes, 1. e. to accomplish a more thorough separation of pulp subjected to flotation.

Cationic reagents ar water-soluble organic compounds, such for example as salts of heavily loaded primary, secondary, tertiary r quaternary arnines that yield large positive lipophile ions and mildly negative hydrophile ions in aque ous solution. Such compound facilitate flotation of numerous minerals both metallic and non-metallic, but particularly quartz. Compounds of the cationic reagent type include octa- 'decy1 amine hydrochloride, hexadecyl amine hydrochloride, cetyl methyl amine hydrochloride, cetyl dimethyl amine hydrochloride, cetyl trimethyl amine hydrochloride, cetyl pyridinium bromide, octadecyl dimethyl phenyl ammonium chloride, and similar amine salts having a nitrogen atom derived from an NH; radical as a nucleus and with one or more of the hydrogen atoms replacedby organic groups. The nuclear nitrogen and the attached organic groups form in aqueous solution the large cation from which the group of reagents takes its name.

Although cationic reagent may be employed to facilitate the flotation of minerals of metallic lustre, including metallic sulfides such as galena, they find their major application in the flotation of quartz from non-sulfide minerals such as calcite, barite, fluorspar, iron oxide and rock phoshate. The application of cationic reagents to mineral separation, however, has been limited because the cationic reagents, in general, are inwith separation of the minerals present in the if this water is returned to the assignor to South- Baltimnre, -Md.,

cationic reagents i aggravated, in manyore dressing operations, by thelack of a sufllcient supply of absolutely slime-free water. In many o erations it is necessary to recover water from treated pulp (-by means-of thickeners or the like) and return the water to the flotation or other mine al separation treatment.. Even the small slime present in the apparently from a thickener often is suiiicient to have a marked deleterious effect upon selectivity and consumption of cationic reagents, flotation circuit. even though considerable effort is made to deslime the pulp prior to adding the cationic reagentsand even though the pulp be subjected to agitation or attrition prior to desliming so a to remove "slimable material as well as actual slimes, an irreducible proportion of slimes ordinarily will remain in the pulp and will interfere with separation by flotation and increase reagent consumption.

As a result of my Consequently,

investigations, I have disemploying cationic reagents can be improved substantially (even when the pul undergoing or slimable material) by employing an ionization inhibitor to restrict the ionization of the cationic reagent present. The substance employed as an inhibitor may be added to the cationic reagent either before or after the incorporation, of the reagent in the pulp, and may reduce'the ionization of sufficiently selective and in many cases do not bring about an adequate separation of the gangue Thus, a substantialproportion of the valuable mineral usually is floated off with quartz gangue in the tailing, while a substantial proportion of the quartz remains behind with the valuable mineral in the concentrate to the end that recovery and ratio of concentration of the valuable mineral are low.

that will permit cationic reagents to bring about a requisite degree of separation of the minerals in the pulp. The problem of accomplishing slime removal adequate to the economic application of the reagent with or without affecting its water solubility. By the expression ionization of the cationic reagent as' used herein and in the claims I intend to refer to the ionic concentration in the solution or pulp at a given time. Thus when reference is had to "reduced or restricted" ionization of the cationic reagent, it is intended that such a reference shall embrace conditions wherein the concentration of ions of the original catalytic reagent in the solution is diminished, whether the diminution is due to a common ion effect, the formation of a soluble complex ion having a lower ionization constant, the formation of a less soluble compound providing'a decreased proportion of dissolved reagent capable'of ionizing, or to any other cause.

Suitable ionization inhibitors for use in the practice of the invention may be classified as follows:

I. Compounds that react with the cationic reagents to form other cationic-active compounds of diminished water solubility and consequent diminished ionization. Examples of such compounds are:

A. Sulfuric acid, alkali sulfates, alkaline earth sulfates and other compounds yielding -S04 ions yielding SiFa ions stances. especially when diminished solubility,

' proportions were required to D. Sodium fluosilicate and other compounds in aqueous solution;

E. Chloroplatinic acid;

F. Compounds, such as potassium perchlorate, that yield ClO4 ions in aqueous solution;

G. Compounds, such as alkali and alkaline earth hydrates and ammonium-and alkylated ammonium hydrates, that yield -.OH ions in aqueous solution; and

H. Molybdic acid.

II. Compounds that restrict ionization of the cationic reagent without necessarily afl'ecting its water-solubility:

A. Compounds which react witl. the cationic reagent to form compounds that are no less water-soluble, but that ionize to a lesser extent, for example:

1. Metal-ammonium complexes such a cuproammonium nitrate and zinc-ammonium nitrate;

2. Fierrocyanides, such as potassium ferrocyanide;

B. Water-miscible (i. e., water-soluble or water-dispersable) non-electrolytes that limit ionization of cationic reagents without apparent chemical union, for example, carbohydrates such as sugars, dextrines and starches in the form of hydrous Jellies.

As indicated above, the ionization inhibitor may be with the cationic reagent either before or after its incorporation in the pulp. In some inthe reagent is of type I and reacts to produce a cationic reagent of it is desirable to carry on the reaction prior to, incorporation in the pulp.

Cationic reagents are, in general, active in both acid and alkaline pulps-although some of the reagents that are positively charged in acid solution acquire a negative charge in alkaline solution and vice-versa. tice oi the invention, the pH of the pulp should be such that the cationic-activity of the reagent is preserved, and in general. the pH of the pulp should be that which is most suitable in the particular flotation operation-minus the ionization inhibitor. In other words, the inhibitor should be employed without materially altering the pH of the pulp. Many of the reagents are substantially neutral in character and can be employed in relatively large. proportion without aflfeoting the pH of the pulp. Others, for example, sulphuric acid and alkali metal hydrates, are strong acids and bases, and would have a pronounced effect upon hydrogenion concentration if large inhibit ionization. However, these inhibitors are of such nature that only a small proportion ofthem is requireda proportion which is so small, in terms of the quantity of pulp, that they may be employed without substantially changing the pH oi the pulp.

to produce a modified compound that is sparingly soluble in water, it may be desirable to react the two to form a precipitate of the modified compound which is introduced into the pulp after it has been washed to free it of excess acid.

To summarize, my invention contemplates the improvement in mineral separation involving the Consequently, in the prac- If the inhibitor employed is strongly acid or alkaline and is of the as debris or -recovery plant feed,

- attrition away from another in presence of a cationic rerestricting the ionization flotation of one mineral an aqueous pulp in the agent which comprises .of the reagent, i. e., preventing the-reagent i'rom ionization to the extent means of an ionization inpossible at the prevailing pH of the pulp, by hibitor. This ionization inhibitor is of such nature and is employed in such proportions that it has substantially no efl'ect .upon the pH of the pulp. The invention is particularly useful inv tion of ,a variety of minerals by froth flotation in the presence of a cationic reagent.

Hereinafter the practice and advantages of my invention are illustrated with reference to the flotation of quartz from'Fiorida rock phosphate, in a substantially neutral pulp, but it will be understood that the-invention may also be applied in the flotation of quartz from other minerals, for example, calcite, barite, fluospar and iron oxides as well as to the flotation of other min-' erals, including sulphides such as galena. In short, the invention may be applied with ad vantage to any mineral flotation operation that employs a cationic reagent. It should be understood, also, that the invention may be practiced with substantially all cationic reagents and in pulps of different hydrogen ion concentrations.

considerable slime had been removed in a washery. Such material is known depending upon whether it isdiscarded or subjected to furtherphosphate recovery operations and consists essentially of silica and phosphate sand together with a small proportion of free slime and a larger proportion of slimable material, i. e., soft friable material attached to the larger particles of silica and phosphate.

Conventional desliming treatment will remove the free slime from such feed, but the slimable material is not removed by washing, etc'., unless the feed pulp is given a preliminary agitation or treatment calculated to free the slimable material from the larger and harder particles. In most instances the feed was subjected to such an attrition treatment followed by washing with clear water before any flotation reagents were added. Other factors remaining the same, the longer the attrition treatment, the more thorough the removal of slimable material, so the duration of the attrition treatment is an index of the freedom of the washed feed with respect to actual and potential slimes. In some instances, the eifect of .slime upon the process was determined by returning to the feed a portion of the slime removed.

The cationic reagent employed in all of the examples was a mixture of hexadecal and octadecyl ammonium chlorides sold under the name AMCL-1180-B by Armour and Company, but

. referred to hereinafteras Cl-B in the interest agent subsequent from the p The pulp was then condiasst-toe The calcium sulfate employed inthe foresoins example is, an ionization inhibitor or'type 1A (ante) in that it tends to react with the cationicreagent to reduce the latters water-solubility and.

consequently its ionization. That the inhibitor was effective in improving the selectivity of the its ionization. Thereafter the frother was added and the pulp was diluted with water. subsequent froth flotation, the silica was removed as a dense froth which was dewatered and dried in the conventional manner to give a product designated hereinafter as "talling. The phosphate product or concentrate remained in the pulp. Any variations from the above-described standard procedure are indicated in the examples.

EXAMPLE I The ionization inhibitor employed in this example was calcium sulphate in the form of gypsum (CaSO4.2H2O) ground to pass 80 mesh. It was mixed with the deslimed pulp, which contained about 60% solids, in the proportion of 5 pounds per ton of solids, and then a water emuls'ion of the cationic reagent and collector was mixed in. Agitation of the pulp was continued until the dark color of the emulsified oil was no longer apparent. Thereafter the pulp was diluted; the frother was added; and froth was re- Durin process is indicated by the 1m thatthe recovery ofphosphatewas raised from 61.1% to 73.6%. Exmrus 2, 3, 4, 5 I

In this series of tests, the efilcacy of various ionization inhibitors of type IA was determined. In Example 2, gypsum was again employed'as an inhibitor and was mixed with the'pulp prior to the addition of the other reagents.

In Example 3, gypsum was also employed, but

was mixed with the emulsion of cationic reagent moved in a flotation period enduring for from 1 to 2 minutes.

For purposes was subjected to exactly the same treatment except that no ionization inhibtor was employed.

Further data, including the results of the treatment are given in Table 1.

Table 1 Example 1 ionization Blank restricted by calcium sulfate Desli'ming Attrition timemins. l6 l6 Flotation Per cent solids in pulp during conditioning. 60 Ionization inhibitor-kind None Gypsum lbs./ton dry iced 5.0 Cationic reagent-C1-B" lbs./ton dry teed 0.2 0. 2 Collector-Petroleum fuel oillbs./ton dry ieed 1.5 1. 5 Frother-du Pont B23"-lbs./ton dry iecd 0. 3 0. 3

Analysis Feed:

Per cent B. P. L. 32. 81 32. Per cent insol 58. 59. lime:

Per cent B. P. L 57. 22 57. Per cent insol 24. 75 24. Concentrate:

Per cent B. P. L 78. 55 77. Per cent insol 3. 47 6. Telling:

Per cent B. P. L 12.79 6. Per cent insol 83. 34 89. Per mi: dialnbatio'n l2. 7 13.6 61. l 73. 6 26. 2 l2. 8

slime, s. 1 a. 2 Concentrate 1. 5 3. 2 Telling 95. 4 93. 6

1 Bone phosphate oi lime.

'35 of comparison, a "blank sample and collector. prior to addition to-the pulp.

In Example 4, the inhibitorwas sulfuric acid. To 30 cc. of 1% solution of the cationic reagent (equivalent to 0.3 pound of reagent per ton of solids in the pulp) there was added 5 cc. of a 5% H2804 solution. The resulting precipitate was washed to free it or excess acid, and the washed precipitate and the collector were mixed with the p lp.

In Example 5, the ionization inhibitor was potassium sulphate, which was mixed intothe pulp prior to the addition of the aqueous emulsion of cationic reagent and collector.

The blank sample was subjected to the same 7 treatment as the others, except that no ionization inhibitor was employed.

The eflect of the various inhibitors and of the manner in which they were used i shownin the following table.

Table 2 Examples No. Blank Dulimina Attrltiontime-minutes. 15 15 15 1s l5 Flotation Percent solids in pulp during conditioning... 50. 50 59 50 50 Ionization inl1ibitoI:---

kind None CaSOi CBSOl H1804 K lbs.lton. 5 5 1 Cationic reagent-"Cl- B"lbs./ton 0. 3 0.3 0. 3 0. 3 0.3 Collector-petrol. iuel oil-lbs. ton 1. 5 l. 5 1. 5 1; 5 l. 5 Frother-du Pont B- 23lbs./ton 0. 3 0. 3 0. 3 0. 3 0. 3

Analilsis eed:

PercentB. P. L 29.86 30.60 29.88 30.38 31.27 Per oentinsol 62. 59 61. 53 62. 19 61. 51 61. ll Concentrate:

Per cent 13. P. L- 75. 72 78. 82 76.31 78.07 78. 41 Per cent insol 7. l5 3. 60 6. 28 3. 27 4. 42 Taillng:

Per cent B. P. L. '12. 58 9.37 5.22 9. 94 9. 22 Per cent insol 83. 54 87.06 92. 55 86. 51 87. 58

Percent distribution Concentrate 69. 4 78. 8 88. 7 77. 2 80. 0 Telling 30. 6 21. 2 ll. 3 22. 8 20. 0 Insol Concentrate 3. l 1.8 '3. 6 1.6 2. 3 Tailing 96. 9 98. 2 96. 4 98. 4 97. 7

In another test, lead sulphate in the proportion of 5 pounds per ton of solids was incorporated ingthe pulp, but was found to be substantially stantially less than that g and hence yields an ineirective quantity of S04 inenective as an ionization inhibitor, probably because its water-solubility is too low-i. e., suboi' calcium sulphateions to react with the cationic reagent.

It is to be observed that all 01 the compounds yielding substantial proportions of S04 ions are eil'ective in raising the selectivity of the ilotation process, and that such compounds with relatively low water-solubility (for example, calcium sulphate) are particularly efi'ective if they are mixed with the cationic reagent in relatively concentrated condition, prior to dilution with the pulp.

It is also to be observed that the eil'ect oi the sulfuric acid is not to be attributed to a change in the hydrogen ion concentration in the pulp, for the acid in excess of that required to react with the cationic reagent was not permitted to enter the pulp.

EXAMPLE 6 This example illustrates the efiect of S2O: ion in inhibiting the ionization or cationic reagents. -The sodium. thiosuliate employed is an inhibitor or type 10 and was added to the deslimed pulp during the conditioning step. Other pertinent data or the test are given in Table 3, which also shows the results obtained in a blank test, identical in all respects to that oi. Example 6 except thattno ionization inhibitor was employed.

Table 3 Blank Exnanple Dealimina Attrition time-minutes 15 15 Flotation Percent solids in pulp during oonditioning.-.. Ionization inhibitor-kind "15.75- None N m8 n-- Cationic reagent-Cl-B"-lb.lton 0.3 0. Collector-petrol. ruel oillb./tcn 1. 5 l. Frother-du Pont "B23"lb./ton 0.3 0.

I Analysis Feed:

Percent B P L 29.86 31.17 Percent insol 62. 59 60. 71 Concentrate:

Percent B P L 75.72 75. 96 Percent insol 7. 7. 01

n Pa eant B. P. L 12. 58 6 55 Percent insol 83. 64 90 33 Percent distribution B. P. L.:

P rntn 38.: ?gg Telling lnsol.:

Concentrate 3.1 4. 1 Tail] 96. 9 95. 9

the S:Oa ion has a upon the selectivity of As the table shows, marked beneficial efiect the process.

EXAMPLE 7 Thisexample demonstrates the eflect of ion- "Daxad (n. P. n)

water solution of the cationic reagent Cl-B,"

a yellowish precipitate is formed.

- In Example! and in the blank testrun for comparative purposes, the pulpwas washed thoroughly after a 10-minute attrition treatment, but a 5% aqueous suspension of slime was added to'the resulting de-slimed feed, so as to give 1.5 pounds present in the pulp. In this way it was possible to .demonstrate that, the ionization inhibitors have a beneficial eiIect upon the selectivity of the process even when substantial slimes are present.

In 'Example '7, the organic sulionate Daxad No. 23 in the proportion 01' .25 pound per ton of solids was mixed with the slime-bearing pulp immediately before the emulsion oi cationic reagent and collector was incorporated. The blank received identical treatment except that no ionization inhibitor was employed. The the comparative tests are given in Table 4.

Table 4 Blank Example 7 Dealiminq l Attrition time-minutes"; i0 10 Flotation Percent solids in pulp during conditioning. 50 50 Ionization inhibitor-1115,11}? None Band #23 on 2' Cationic Reagent Cl-B"lb./ton. 3,5 3 Ccllectorpetrol. fuel oillb./ton 4 l. 6 l. 6 Frother-du Point B23"- lb./ton 0. 3 3

Analysis Feed:

Per cent B l 28. 36 30. 84 Per cent insol 63. 94 61. 99 Concentrate:

Per cent 13. 62. 76. 69 or cent insol 23. 27 6. 94

8: Per cent B. p. l 6. 99 6. 77 Per cent insol 89. 32 v 90. 93

B. P. L.:

Concentrate 84. 8 85. 6 lailin l5. 2 l4. 4 so Concentrate 14.0 3.6 Tailing 86. 0 96. 4

l 1.5 lb'Jslime per ton returned to de-slimed iced.

concentrate which was produced despite the presence of a relatively large proportion of slime. Thus, the concentrate grade was raised from 62.65% to 76.69% bone phosphate of lime EXAIPLI 8 The use 01' a-reagent of type II-A, specifically cupro-ammonium nitrate, is illustrated by this example.

The sample and the blank treated-for purposes of comparison were subjected toattrition treatment for 6% minutes and then washed. This removed some of the slimable material from the pulp, but in order to test the efiect of free slime, 2 pounds (dry) of slime per ton of solids were returned to tioning.

The cupro-ammonium nitrate (equivalent to .12 pound Cu .per ton solids in the pulp) was mixed with the pulp prior to conditioning with the emulsion of collector and cationic reagent.

The results of the tests are shown in Table 5.

results of v the extremely small the high grade of the e the pulp samples prior to condi- The principal beneficial effect or the ionization inhibitor was to raise the grade of the concentrate (from 43.40% to 52.93%) while increasing the proportion of the total insoluble matter collected' in the tailing (from 49.7% to 69.8%). Further benefits from the use of cupro-ammoniumnitrate and similar inhibitors can be obtained by carrying out the flotation in the presence of less slime or slimables or by employing a greater proportion of inhibitor.

EXAMPLES 9,

The feed employed in these examples and in the comparative blank" had been largely cleaned with respect to free slime in a large Denthe inhibitor was mixed with the water emulsion of the collector and the cationic reagent prior to incorporation of the pulp. That both reagents were effective in'improving the selectivity of the process is shown in the following table.

Table 5 Table 6 9 Blank Inmple 9 9 Blank Minin 1 5 9 1o Attrition time-minutes BM 6% mum,

on in r? am in 5 Attrition time-minutes None None None Percent solids pu p uring eon on g- Ionization inhibitor-kin N gr m 10 FWM tmte Per cent solids in during conti t-Cl B lb [to m 35 I 32in 6111155 22136 N w Dextrif s w c on n. i 0 on one agar 8311mm. iuel oil-1b.]ton. 1. 0 l. 0 lbJton 1. 0 1. 0 Frother-du Pont B-Zi"lb./ton 25 Cationic reagent "Ol-B"-lb. n... 0. 3 0. 8 0. 8 Collector-petrol iuel oil-lb. n. '3. 0 3. 0' 8. 0 Analytic 15 Frother-du Pent "B-23"l :on.. o. a o. s o. a Feed:

1; n. P. L 29.94 90.49 Am m 5 can inso 62. 66 02. 24 Feed:

Per cent B. P. L 27. 04 27.69 27. 97 43. 4O 52. 93 nt 64. 61 64. 62 63. 91 47. 40 35. 40

77. 16 76. 87 75. 79 1 9% Z: 6. l3 5. 17 7 09 p e i i roi-oonin. P. L.-. 19.13 19.51 12.88. B P Per'mit distribution Per cent 111801"... 74. 13 83. 08 81. 93 91.0 91. a Per cent diltribuiion 25 B. 1 50.3 0- 2 Concentrate 38. 5 65. 5 65. 1 49.1 69.8 'r or 6 34. a 34.9

lnsoL: Concentrate l. l 1. 9 2. 7 l 2 lbJslime p t n returned to de-elimed feed. '1 98. 9 98. 1 97. 3

amount of an alkaline earth sulphate suflicient to inhibit ionization of the amino compound, and

subjecting the resultant pulp to froth flotation.

2. The method of beneflciating a phosphate ore as set forth in claim 1, in which the ionization inhibitor is calcium sulphate.

3. The method of beneficiating a phosphate ore as set forth in claim 1, in which the ionization inhibitor is calcium sulphate and is added to the pulp in an amount equal to about 5 pounds per ton of solid material in the pulp.

EDWARD J. ELLIS.

cmmmcms 0F CORRECTION. 4 c I Pa tent No. 2,527,Lo8.' A ust 21;, 1915. EDWARD J. ELLIS.

It is hereby certified that ez 'ror appears in the printed apecifiootien of the above numbered pa'tent requiring correction aefollowa: Page 2, geef "0nd column, line 5, for "ionization z ead "ionizing"; line 27, for "fluo spar" reaa -fluorspar--; page 1;, firet column, line 112, Tab1e'5, for "M 80 read --Na S O page 5, first column, l1ne19, Table 5, for "Rail- 1115" read -.-Ta5 .l1ngand second column, line 51, before "dextrine'! insert ----the---; and that the said Letter-a Patentshouldbe read with this correction therein that the same may conform to the .re'coz d of the case in the Patezit Office. I

Signed and aea led this 9th day of November, A. D. 1914.5.

Heni'y Van Arsdale, (Seal) I Acting Commissioner of Patents. 

